It is well known to use non-halogenated flame retardants or fillers to augment the mechanical properties of olefin polymer compositions. Polyolefins filled with organic and inorganic materials have shown high performance, recyclability, and flexibility in design and fabrication. There is a need, however, to couple the polar non-halogenated flame retardants and fillers with the non-polar olefin composition in such applications, to increase the interfacial adhesion between the non-halogenated flame retardant or filler and polymer matrix, since poor interfacial adhesion often results in poor mechanical properties of the polymer blends. U.S. Pat. No. 5,324,755 discloses the use of olefin polymers chemically modified with ethylenically unsaturated carboxylic acids or derivatives thereof, such as acrylic acid, maleic acid, itaconic acid, maleic anhydride, citraconic anhydride and itaconic anhydride, as coupling agents. U.S. Pat. No. 3,414,551 discloses modifying propylene polymers with maleic anhydride, which can be used as adhesives. However, conventional coupling agents for non-halogenated flame retardant-containing and filled polyolefins do not significantly modify the rheological properties of the polymer blends in the polymer matrix. As a result, the potential polymer-processing window is narrowed due to its flow characteristics. In addition, conventional coupling agents do not typically improve the dispersion of non-halogenated flame retardants or fillers and if they make any improvement at all, it is minimal. Improving such dispersion would be desirable since it enhances the uniformity of mechanical properties throughout the polymer material, as well as increasing the effectiveness of commonly used additives, such as colorants and flame retardants that also can be present in the polymer composition. Thus, there continues to be a need for coupling agents in non-halogentated flame retardant or filler-containing olefin polymer compositions that can modify the rheological properties of the polymer matrix, and which may also function as a dispersant for additives.
It has unexpectedly been found that the irradiated, oxidized olefin polymer coupling agents of the present invention provide distinct advantages in the coupling of non-halogenated flame retardants, fillers or mixtures thereof in the olefin polymer matrix; providing an improved balance of physical properties to compositions containing such an olefin polymer matrix, while also improving the dispersion of the non-halogenated flame retardants, fillers or mixtures thereof.